Osteotomy is a surgical operation during which an incision is made in the bone at a specific location in order to correct the alignment of this bone. Osteotomy can be applied to various bones in the human or animal body, but most commonly to the proximal or distal femur, the proximal or distal tibia, the proximal or distal humerus, the forearm and in some cases, the smaller bones like the clavicle, fingers, or toes. The correction is usually carried out on the basis of a predetermined axis. The most common reasons for osteotomic intervention are traumas or congenital abnormalities that affect the joints or bones leading to pain, discomfort, or further complications.
Depending on whether a positive or negative bone inclination adjustment is required, osteotomy can be divided to two realignment procedures. The first type, opening wedge osteotomy, involves creating an incision that is then spread-open using a spreader device to create a broadened wedge-shaped opening which can be filled with a bone substitute. In the second type, closing wedge osteotomy, two incisions are made into the bone to create a wedge-shaped piece that is removed and the gap that is left is closed. Both corrections are then stabilised by fixing the bone ends together with an implant, usually a plate screwed above and below the place where the wedges were formed.
Osteotomy has to be done correctly in the first attempt, given the extensive recovery time and potential complications. The probably most commonly performed osteotomy is done in the vicinity of the knee joint (knee osteotomy). There are currently several devices known in the art serving the exact purpose of aiding knee osteotomy, cf. US20020133157, US2008262500, US2002165552. Several of them make use of hinged spreaders whose opening angle is controlled and optionally measured using a screw-based system cf., EP2036509 or US20050273114. Several devices are equipped with more exact protractors for reading of the angle and may use swinging adjustable pins for stabilising the protractor on the uneven bone surface while estimating the measure of the necessary correction angle, cf. US2008195099, FR2679126. Several of these devices allow a relatively precise calculation of the necessary correction angle during making and spreading the wedge incision, but once such device is removed, the surgeon is left with no exact guideline or points of reference allowing him to control that the pre-determined angle is not being changed during the fixing procedure. Usually, the surgeons have to rely only on 2D X-ray pictures that are being extensively taken during the operation, as none of the currently-available devices provides fixed reference means for guiding the surgeon during fixation of the wedge made in the bone after the angle measuring device has been removed to make way for fixation means. Therefore, there currently exists a need for an economical simple device that would not only uniformly allow the precise calculation of the necessary correction angle, but would also provide means for maintaining this pre-determined angle constant during the fixation of screws and plates, thus also advantageously allowing reduced use and exposure to X-rays.